The invention relates to improvements in apparatus for regulating the operation of certain constituents in the power trains of motor vehicles, for example, for regulating the operation of continuously variable transmissions in dependency upon the changes of one or more parameters of the motor vehicle, of its power train and/or other variables. Still more particularly, the invention relates to improvements in torque regulating apparatus which employ so-called torque sensors.
Commonly owned U.S. Pat. No. 5,169,365 (granted Dec. 8, 1992 to Oswald Friedmann for xe2x80x9cPOWER TRAINxe2x80x9d) discloses a power train wherein the engine of the motor vehicle transmits torque to a continuously variable transmission (CVT) by way of a rotary torque sensor which is connected to the output of a pump serving to supply a pressurized hydraulic fluid. The torque sensor acts as or includes a valve and serves to transmit torque from the engine to the input element of the transmission. As a rule, the valve of the torque sensor comprises or defines a plenum chamber and is designed to transmit at least a portion of the torque between the output element of the engine and the input element of the transmission. Reference may also be had to commonly owned published German patent application Serial No. 195 44 644. The disclosure of each and every patent and each and every patent application (including the commonly owned German priority patent application Serial No. 198 12 033.8 filed Mar. 19, 1998) identified in the specification of the present application is intended to be considered as having been incorporated herein by reference.
As a rule, the torque sensor which is utilized in conjunction with a continuously variable transmission serves to eliminate or prevent the development of play between the component parts of the transmission in dependency upon the load and/or torque. Such elimination of play ensures reliable engagement between the lateral surfaces of an endless flexible element (such as a chain or a belt) and the adjacent conical surfaces of the flanges forming part of adjustable pulleys or sheaves in the continuously variable transmission. Thus, the torque sensor can ensure the development and a continuous transmission of a force the magnitude of which is dependent upon load and/or torque and which prevents the flexible element and the pulleys of the continuously variable transmission from slipping relative to each other. As a rule, the regulation of forces acting between the marginal surfaces of the flexible element and the conical surfaces of the flanges forming part of adjustable pulleys is effected by hydromechanical means.
The establishment of an optimal frictional engagement between the flexible element and the pulleys of the continuously variable transmission is desirable and important because the selection of an optimum frictional engagement brings about substantial savings in fuel (in comparison with the fuel consumption when the frictional engagement between the flanges of the pulleys and the flexible element is excessive). On the other hand, if the frictional engagement is insufficient, the flexible element and the pulleys are likely to slip relative to each other which entails unnecessary and highly pronounced wear affecting the useful life of the power train. The hydromechanical torque sensor is intended to select an optimum frictional engagement between the endless flexible element and the pulleys such as ensures savings in fuel, i.e., to select a frictional engagement which is best suited for the transmission of torque at an optimum rate.
It is already known to design a torque sensor for use in conjunction with a continuously variable transmission in such a way that it employs a valve which controls the pressure of fluid in a plenum chamber in response to abrupt changes of transmitted torque. This is accomplished in that the valve seals a path for the flow of hydraulic fluid from the chamber into the sump, a path which is defined in part by a flow restrictor. The sealing step takes place in response to a shifting of a mobile part of the torque sensor. As a rule, the valve is a pressure limiting or pressure relief valve which regulates the fluid pressure in the plenum chamber in dependency on the magnitude of the torque to be transmitted as a function of the required transmission ratio as soon as the plenum chamber is sealed from the outlet leading to the sump.
The minimal fluid pressure which a conventional torque sensor employing a pressure relief valve can select for the fluid in the plenum chamber is determined by the remaining hydrodynamic pressure in the conduit or port leading to the conduit or port connecting the plenum chamber with the sump. Thus, one can realize or achieve a fluid pressure which is proportional to the momentarily prevailing torque only after the sensor already transmits a torque of predetermined minimum magnitude, i.e., when the fluid pressure reaches or exceeds a predetermined value.
An object of the invention is to provide a novel and improved torque sensor which can be utilized in conjunction with a continuously variable transmission.
Another object of the invention is to provide an apparatus which is associated with a transmission in the power train of a motor vehicle and embodies the improved torque sensor.
A further object of the invention is to provide a torque sensor which is designed to ensure that an optimum fluid pressure necessary to ensure a desired mode of operation of adjusting units utilized in a continuously variable transmission will be available under all or practically all circumstances which are anticipated in actual use of a power train embodying the transmission.
An additional object of the invention is to provide a novel and improved valve for use in the above outlined torque sensor.
Still another object of the invention is to provide a torque sensor which can be utilized as a superior substitute for conventional torque sensors in the power trains of motor vehicles, especially in power trains which embody continuously variable transmissions.
A further object of the invention is to provide a method of influencing the operation of a torque sensor in the power train of a motor vehicle.
Another object of the invention is to provide a relatively simple, inexpensive, compact and highly versatile torque sensor for use in conjunction with a transmission in the power train of a motor vehicle.
An additional object of the invention is to provide a novel and improved system of valves for use in the hydraulic circuit of an apparatus employing the above outlined torque sensor.
Still another object of the invention is to provide a combined torque sensor and torque transmitting device which can be utilized, with appropriate controls therefor, in the power train of a motor vehicle, particularly between the rotary output element of the prime mover and the input element of a transmission, such as a continuously variable transmission.
The invention is embodied in a rotary torque sensor which is arranged to transmit torque between rotary input and output elements, e.g., between a shaft which is driven by the camshaft or crankshaft of an internal combustion engine and a shaft which transmits torque to one adjustable pulley of a continuously variable transmission. The improved sensor has a plenum chamber and comprises a pressure reducing valve arranged to control the flow of a hydraulic fluid (e.g., oil) into and from the chamber. The valve has at least two valve members at least one of which is movable relative to the other valve member to thereby vary the pressure of fluid in the chamber and to thus influence the capacity of the torque sensor to transmit torque between the input and output elements. The torque sensor further comprises or cooperates with a pump or another suitable source of pressurized fluid which is connectable to the plenum chamber by the aforementioned valve.
In accordance with one presently preferred embodiment, the valve has an inlet opening connectable to the aforementioned source of pressurized fluid, a first outlet opening which is connectable to a fluid collecting device (e.g., a sump), and a second outlet opening connectable with at least one adjusting unit (such as a cylinder-and-piston unit) of a transmission, particularly a continuously variable transmission.
One of the openings can be provided in the one valve member, and such one valve member can be arranged to rotate with the input element. Alternatively, at least one of the openings can be provided in the one valve member.
The valve can be operated in such a way that the one valve member is movable to at least one position in which at least two of the openings (such as the inlet opening and the first outlet opening) are sealed.
Alternatively, the arrangement can be such that the one valve member is movable relative to the other valve member to at least one position in which the inlet opening and the first outlet opening are at least partially exposed to permit pressurized fluid to flow from the source into the plenum chamber and to flow from the chamber to the fluid collecting device.
Still further, it is possible to design the valve in such a way that, when the one valve member is moved relative to the other valve member to at least one preselected position, the inlet opening is sealed to prevent pressurized fluid from flowing from the source into the plenum chamber and the first outlet opening is also sealed to prevent fluid from flowing between the chamber and the fluid collecting device.
It is also possible to design the valve in such a way that the one valve member is movable relative to the other valve member to at least one position in which the inlet opening is sealed to prevent pressurized fluid from flowing from the source into the plenum chamber while the first outlet opening is at least partially exposed to permit fluid to flow between the chamber and the fluid collecting device.
The one valve member and the other valve member can be provided with first and second substantially radially extending profiled portions which confront each other, and such torque sensor can further comprise one or more torque- and force-transmitting elements (e.g., in the form of spheres) between the two profiled portions. The other valve member can be connected for rotation with the input element, and the one valve member can be connected for rotation with the output element of the torque sensor. The magnitude of the force which is being transmitted by the at least one torque- and force-transmitting element is or can be at least substantially proportional to the pressure of fluid in the plenum chamber.
It is also possible to design the valve in such a way that it has an inlet opening connectable with the source of pressurized fluid and an outlet opening connectable with at least one adjusting unit of a transmission, such as a continuously variable transmission.
At least one of the two openings is or can be provided in the other valve member which is arranged to rotate with the input element. It is also possible to provide at least one of the two openings in the one valve member which is arranged to rotate with the output element. Still further, at least one of the two openings can be sealed in response to movement of the one valve member relative to the other valve member.
The valve with only two openings can be designed in such a way that the one valve member is movable relative to the other valve member to at least one position in which at least the inlet opening is at least partially exposed to permit pressurized fluid to flow from the source into the plenum chamber. It is also possible to move the one valve member to a position in which only the inlet opening is at least partially exposed to permit pressurized fluid to flow from the source into the plenum chamber.
Still further, and as already described in connection with the embodiment wherein the valve has an inlet opening and two outlet openings, the valve members of the valve having an inlet opening an one outlet opening can be provided with first and second substantially radially extending profiled portions contacting at least one force and torque-transmitting element (such as a sphere) which also serves to shift the one valve member relative to the other valve member. The one valve member is axially movably but non-rotataby connected to the output element, and the other valve member is or can be fixedly secured to the input element. The magnitude of the force being transmitted by the at least one force- and torque-transmitting element is or can be at least substantially proportional to the pressure of fluid in the plenum chamber.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved torque sensor itself, however, both as to its construction and its mode of operation, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.